At present the use of escalators and other transport means between two zones, preferably at different heights, allow people or goods to be transported continuously, is common.
One example are escalators arranged between two heights (e.g., between two floors of a building) since they are efficient and comfortable, particularly where there is an abundant and constant circulation of people, for example in railway stations, airports, shopping centres or public buildings. Other means for transporting people, such as lifts, service lifts and elevators have a high transfer capacity for each journey, which can be at a great height covering several floors, but unlike escalators they do not allow for continuous transit.
In an implementation, when escalators are utilized to transport people, they may be configured as a series of steps arranged on a drive chain, moved by a motor geared to said chain and controlled by a control unit. The steps and the drive chain travel via at least one advance track that configures the travel direction, returning via a return track, which is commonly hidden, with intermediate transition zones of said series of steps in between. At least the advance track is made up of a set of lateral guides in which the steps are moved by means of bearings on both sides of the step. The steps may be rigid with a tread and at least one riser.
In such an example, the user may position himself/herself at the entrance of the advance track until he/she observes a step exiting from the chain that is moving continuously, he/she steps onto it and waits for the step to move him/her toward the other end of the advance track, either upwards or downwards. A problem lies in the fact that the steps have a tread with a specific length which is limited by the height of the step riser or height difference between two consecutive steps which must be small enough to allow a person to move along the escalator feasibly in the event that the latter stops.
Typically, this length is about 45 to 65 centimeters, which prevents people with reduced mobility, such as people in wheelchairs, walking frame users, people with crutches or baby pushchairs from using the escalator.
In order to overcome the limitations, alternative transport means have been proposed. For example, the use of a lift, which is limited to vertical elevation, is common while the use of a ramp is not possible according to current regulations for gradients greater than 10% in the case of greater possible inclination. Platforms or stair lifts do not present these inclination limitations, therefore they can cover those intermediate inclinations with respect to the previous solutions, but they tend to be slow and, often require the assistance of other people or the use of an activating key with the inherent setbacks associated therewith.
Alternative escalators have been developed to overcome said difficulties by means of the vertical movement of at least one of the steps in order to position it at the same height as that of a conventional previous or subsequent step so that the sum of the length of both steps sets up a coplanar platform of greater length.
U.S. Pat. No. 5,353,907 for a “Dual Purpose escalator for wheelchair” describes a dual-purpose escalator comprising a plurality of specialized steps for loading a wheelchair. The escalator comprises an apparatus that activates said specialized steps so that in a wheelchair loading operation, an assembly of three steps alters its configuration. A first specialized step, subsequent to a central step, comprises a gear and a multiple scissor-type mechanism that allows the tread to be elevated to the correct height in order to be coplanar with the previous step. At the same time, a specialized step, previous to the central step, comprises a mechanism that allows it to fold down at a suitable angle to expand the length of the previously assembled platform. This escalator allows the mentioned formation of an expanded platform but of incomplete length with respect to the three steps involved. In addition, the specialized steps are heavier due to the mechanisms that they incorporate, thus such can cause an imbalance of the drive chain. Also, the engagement of the movement mechanisms of the specialized steps with the mechanism that allows it to be activated at the beginning of the advance track can fail.
Another problem that conventional escalators present is that they do not permit simultaneous transport upwards and downwards. This is mainly due to the fact that the return track of the chain of steps is carried out under the advance track, in the reverse direction.
U.S. Pat. No. 4,411,352 for a “Racetrack escalator” describes an escalator in which the return track is arranged parallel to a lateral of the advance track, thus both are useful, namely one track for going up and the other track for going down. On this escalator the transition zones arranged between the ends of the tracks are configured by a horizontal turn of 180 degrees under a platform that allows entrance or exit. The steps have an approximately parallelepiped shape and they comprise sets of bearings allowing their movement along guides, while between each two steps is a linkage element with two mounting holes that are respectively arranged on two existing vertical pivots on one of the laterals of said steps. The linkage element permits one step to move vertically with respect to the adjacent step, both upwards and downwards, so it can be used both on an ascending and descending track within the same movement direction and to align the turn horizontally. However, this escalator does not have means to allow the transport of wheelchairs or people with reduced mobility using the configuration of an elevating platform with two or more adjacent steps. Furthermore, the space required by this escalator is very wide due to the sweeping stroke of the transition zones and in addition the linkage among steps can be weak, thus the total length of the step drive chain must be especially short in order to reduce stresses.